I really hope this happens.
First of all, it's a great basketball storyline period. Rondo being the best player in the series so far, LeBron stepping up to guard him.
Second of all, I think it's a terrible idea for Cleveland:
1) LeBron is fast, but he's not Rondo quick. No guarantee he can stay in front of Rondo, and he has to worry about sprinting back on defense every play. He might be the fastest 6'8" guy in the league, but Rondo might be the fastest 6'1". There's a difference.
2) Guarding Rondo pulls LeBron far away from the basket. He's at his best on defense when he is roaming and using his reach and quickness.
3) Everyone is talking about Anthony Parker on Pierce (and I agree, that's a 20 point night waiting to happen even from a struggling Pierce). But... who does Mo Williams guard? Ray Ray has a good 4-5 inches on him. If you are Cleveland, you do NOT want Ray Ray guarded by someone he can shoot right over the top of.
4) Rebounding. LeBron is Cleveland's best rebounder and now he's not in position for defensive rebounds. I could see stealing a couple of extra offensive rebounds as a result of LeBron running around instead of being planted in front of Pierce.
I guess there's a chance that LeBron pops out and shuts Rondo down. I mean, if anyone can do anything, LeBron has a shot. But if I had a vote, I'd make it happen both as a C's fan and a basketball fan in general.